This invention relates in general to electrical connections and methods for making such connections and deals more specifically with improved connections and connecting methods particularly adapted for use where high density termination is required.
The employment of soldering and welding techniques for termination of wire conductors and more recently for the termination of high density connectors has come full circle over the past five decades. Soldered and welded terminations, when perfectly executed, represent the optimum of electrical junctions achievable between two metallic materials. Both technologies avoid the use of a third formed metal member required for crimp termination, a special slotted contact member utilized in insulation displacement termination or a stable square post employed in wire wrap termination. These popular options to soldered and welded connections seriously limit the degree of architectural density (contact spacing) achievable with soldering and welding.
Serious disadvantages associated with soldering or welding as a conductor termination method include the use of toxic materials, such as lead, the relatively low production rates associated with manual termination by these methods and the high cost of such automated production equipment. Further, soldered and welded electrical connections afford low resistance to shock and vibration and often lack reliability due to the formation of "cold joints" that are virtually undetectable.
The presently dilemma of employing soldered or welded terminations to facilitate high density electronic packaging is further complicated by established criteria for the use of stranded and solid conductors. During the pre-crimp era of the early 1940's when soldering and welding were the only practical termination options it was generally accepted that soldering was the proper choice for stranded and welding for solid conductor constructions. Subsequent advancements in crimp technology offered viable alternatives for terminating both types of conductors for many industrial, power and electronic applications. However, new design criteria, primarily high density construction, again necessitated choice between solid or stranded wire interconnect options. Since conventional crimp type terminals were not ideally suited for high density termination of wires to connectors, it became evident that a new generation of termination technology would be required to serve the rapid expansion of industry into the computer age of the 1960's.
Two popular technologies emerged. Wire wrap termination, which consists of wrapping a solid small gauge conductor around a sharp cornered post, dominated for about 20 years. A stranded wire technique, which competed for this market, employs a spring terminal applied to the post to trap the stranded wire conductor between the post and terminal in gas-tight relationship.
The aforesaid advancements were accompanied by the creation of the insulation displacement type connector (IDC) to facilitate termination of wire conductors without the need for stripping the dielectric aacket) prior to engagement to the contact terminal. Although occasionally utilized for stranded wire with special provisions, this method is generally accepted only for solid wire termination and, in fact, many large manufacturers prohibit the use of IDC technology for applications where high shock and vibration is likely to be encountered. IDC termination also limits contact spacing or density and where increased density is required staggered multiple rows of contacts must generally be employed with a single termination at each contact position.
Although recent developments in electronic packaging include use of multi-layer printed circuit boards and massive large scale integration (chips) to condense enormous amounts of circuitry, present IDC technology continues to serve these units with input and output power and signals. Now with even more density required to support the next move to microelectronics it has again become desirous to employ solder terminated stranded wire to achieve the flexing reliability required.
Accordingly, it is the general aim of the present invention to provide an improved solderless electrical connection and connecting method which is particularly suitable for use in the high density connection and/or mass termination of electrical conductors. It is a still further aim of the invention to provide improved electrical connections and connecting methods suitable for high production at low cost and having electrically conductive integrity equal or superior to other comparable connections produced by presently available methods.